title: Structural studies on dinuclear ruthenium(II) complexes that bind diastereoselectively to an antiparallel folded human telomere sequence.
abstract: We report DNA binding studies of the dinuclear ruthenium ligand [{Ru(phen)2}2tpphz](4+) in enantiomerically pure forms. As expected from previous studies of related complexes, both isomers bind with similar affinity to B-DNA and have enhanced luminescence. However, when tested against the G-quadruplex from human telomeres (which we show to form an antiparallel basket structure with a diagonal loop across one end), the ΛΛ isomer binds approximately 40 times more tightly than the ΔΔ, with a stronger luminescence. NMR studies show that the complex binds at both ends of the quadruplex. Modeling studies, based on experimentally derived restraints obtained for the closely related [{Ru(bipy)2}2tpphz](4+), show that the ΛΛ isomer fits neatly under the diagonal loop, whereas the ΔΔ isomer is unable to bind here and binds at the lateral loop end. Molecular dynamics simulations show that the ΔΔ isomer is prevented from binding under the diagonal loop by the rigidity of the loop. We thus present a novel enantioselective binding substrate for antiparallel basket G-quadruplexes, with features that make it a useful tool for quadruplex studies.
authors.affiliation: Department of Chemistry, University of Sheffield , Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
authors.forename: Tom
authors.initials: T
authors.lastname: Wilson
authors.forename: Paulo J
authors.initials: PJ
authors.lastname: Costa
authors.forename: Vítor
authors.initials: V
authors.lastname: Félix
authors.forename: Mike P
authors.initials: MP
authors.lastname: Williamson
authors.forename: Jim A
authors.initials: JA
authors.lastname: Thomas
mesh_terms: D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D012428:Ruthenium / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism; D016615:Telomere / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D009942:Organometallic Compounds; D012428:Ruthenium; D004247:DNA